i have a 94 silverado that idles fine in park but trys to stall out in drive or reverse.
I have changed the entire fuel system from the tank to the (TBI) along with the distributer, cap, rotor, plugs, wires,
Have you checked the vacuum line to the vacuum modulator on the transmission? When you put the transmission in Drive or Reverse, it sends vacuum to the diaphram on the modulator and if there' s a leak in the vacuum line, it's going to make the engine run like crap a low speeds.
Search Chevrolet Silverado 1500 Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Chevrolet Silverado 1500 Experts